Absorbable sutures, often called dissolvable stitches, are specialized threads designed to close wounds and incisions without requiring manual removal. These materials are made from substances the body can naturally break down and absorb over time. They hold tissue together until the wound gains sufficient strength to heal independently. Unlike non-dissolvable sutures, which must be removed by a healthcare provider, absorbable sutures are intended to disappear entirely after providing temporary support.
The Mechanism of Dissolvable Sutures
The breakdown of absorbable sutures is a deliberate process based on the material’s chemical composition. Synthetic sutures, which include widely used polymers like polyglycolic acid (PGA) and polylactic acid (PLA), primarily dissolve through hydrolysis. This mechanism involves water molecules within the body’s tissues penetrating the suture material, systematically breaking the polymer chains into smaller, water-soluble fragments. These fragments are then metabolized and eliminated by the body.
Natural absorbable sutures, such as those made from purified animal collagen like “catgut,” are degraded mainly by enzymatic action. Enzymes found in the body’s tissues attack and break down the protein structure of the suture material. The absorption process for all types of dissolvable stitches begins with a gradual loss of tensile strength, followed by complete absorption over a period that can range from a few weeks to several months.
Reasons Stitches May Not Seem to Be Dissolving
A common reason patients believe sutures are not dissolving is a misperception of the expected timeline. Complete absorption can take much longer than generally assumed; for instance, some synthetic materials like polydioxanone (PDS) can take up to 180 days to fully disappear, though they lose their holding strength much sooner. Deep internal sutures are often designed to dissolve slower than superficial ones, providing support for longer-healing tissues.
Another frequent issue is the phenomenon known as “spitting sutures,” where the body actively pushes the material out before it has fully dissolved. This occurs when the suture knot or a segment of the thread is close to the skin’s surface, causing irritation that prompts the body to treat it like a splinter. While this can cause discomfort, redness, or a small raised bump, it is often a localized inflammatory reaction rather than a true failure of the material’s chemical breakdown process. Visible knots on the skin’s surface may simply fall off after a couple of weeks, even if the deeper portion is still undergoing absorption.
Medical Implications of Non-Absorption
When absorbable suture material fails to dissolve as intended, it triggers a biological defense response known as a foreign body reaction (FBR). The immune system recognizes the undigested material as an invader, initiating a chronic inflammatory cascade. This persistent inflammation can lead to the formation of a granuloma, which is a localized, protective wall the body builds around the foreign material.
Suture granulomas consist of immune cells that attempt to isolate the foreign thread. This localized mass can cause chronic pain, tenderness, or a palpable lump at the surgical site long after the wound should have healed. Furthermore, non-absorbed material creates a protected niche, increasing the risk of chronic infection. Bacteria can adhere to the suture surface and become shielded from the body’s immune cells and antibiotics, delaying the overall healing process.
Necessary Steps for Undissolved Sutures
If a patient suspects their dissolvable stitches are not disappearing, the first step is to consult the treating surgeon or healthcare provider. This professional assessment distinguishes between a normal, slow absorption process and a true pathological complication. The provider will examine the wound for signs of infection, such as increased redness, swelling, pus, or a foul odor, which requires immediate treatment.
For threads that are protruding or causing surface irritation—a spitting suture—the provider can perform a simple snip-and-trim procedure to remove the superficial remnant and alleviate symptoms. If a deeper, symptomatic foreign body reaction or granuloma is confirmed, the definitive treatment often involves surgical excision. This procedure removes the persistent suture material and surrounding inflammatory tissue, resolving chronic irritation and allowing the area to heal.